The present invention relates to a method for surface treating and optionally decorating a substrate, and more particularly to a method for powder coating substrates that optionally can be decorated, for example, by sublimation transfer printing or water transfer printing, and a resultant product.
The history of powder coating began in the late 1940s. At that time, organic polymers were being spray coated in a powder form onto metallic substrates. Then, in 1953, Dr. Erwin Gemmer, a German scientist, developed and patented a fluidized-bed method for the processing of thermosetting powder coatings, which is disclosed, for example, in U.S. Pat. No. 2,844,489. Generally, only functional applications, which required a high film thickness, utilized the fluidized-bed method.
The technology of electrostatic powder coating, developed in the United States, and commercialized between 1962 and 1964, soon overshadowed the fluidized-bed method. Between 1966 and 1973 the four basic types of thermosetting resins—epoxy, epoxy polyester hybrid, polyurethane and polyester, which are still used today, were developed and commercially distributed. In the early 1970s, powder coating spread worldwide, but its growth was modest because application systems were expensive. Additionally, the thickness of powder coated films was generally too great for commercial use, as it consumed significant amounts of materials. Further, color change problems, and high curing temperatures, greatly limited the finished product color spectrum and substrate diversity. For example, softer plastics were difficult to powder coat as the temperatures used to set the powder coat often was great enough to deform or melt the plastics.
Since the early 1980s, powder coatings have seen continuous growth, driven by innovations pertaining to the available materials, improved formulating expertise, advances in application technology, and the development of new applications. There remain, however, opportunities to advance powder coating technology.